HENDRICS documentation

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This set of command-line scripts based on Stingray is designed to do correctly and fairly easily a quick-look (spectral-) timing analysis of X-ray data. Among the features already implemented are power density and cross spectra, time lags, pulsar searches with the Epoch folding and the Z_n^2 statistics, color-color and color-intensity diagrams, rms-energy, lag-energy, covariance-energy spectra. The analysis done in HENDRICS will be compatible with the graphical user interface DAVE, so that users will have the choice to analyze single datasets with an easy interactive interface, and continue the analysis in batch mode with HENDRICS. The periodograms produced by HENDRICS (like a power density spectrum or a cospectrum), can be saved in a format compatible with XSpec or ISIS, for those who are familiar with those fitting packages. Despite its original main focus on NuSTAR, the software can be used to make standard aperiodic timing analysis on X-ray data from, in principle, any other satellite (for sure XMM-Newton and RXTE).

What’s new

HENDRICS 8.0.0rc1

  • Compatible with Stingray 2.0.0rc1, which introduced:

    • Lomb-Scargle periodograms and cross spectra are now available

    • Power colors

    • Easy filling of small gaps in light curves with random data

    • Generic timeseries (complex data, multi-dimensional data)

  • HENaccelsearch now has additional options for detrending, denoising and deorbiting

  • An improved Maximum likelihood algorithm as FFTFIT substitute for TOA calculation

  • NASA’s IXPE added to supported missions

  • Better support of Stingray’s native file formats

Older releases

  • Based on Stingray 1.0, bringing a huge bump in performance

  • Following Astropy, Numpy and Scipy, HENDRICS 7.0 is only compatible with Python >3.8

  • Accepts many more file formats for round-trip of Stingray objects, thanks to the new functionality of Stingray.

  • Energy-filtered periodograms

  • A wider range of normalizations available for both HENfold and HENphaseogram, with more options (e.g. smoothing) and higher-contrast color map by default

  • Many fixes to mission-specific files

  • Better info returned by Z/EF searches, including pulse amplitude estimates

  • New upper limit functionality in Z/EF searches with no candidates

  • HENplot now estimates the error of frequency and frequency derivative searches returned by HENzsearch and HENefsearch with option --fast

  • Add ability to split files at a given MJD

  • Much Improved mission support

  • Lots of performance improvements with large datasets

  • Improved simulation and upper limit determination for Z searches

  • Improved candidate searching in Z searches

  • Lots of documentation fixes


More improvements to pulsar functionalities:

  • The accelerated search from Ransom+2002 is now available, to search the f-fdot space through Fourier analysis. It is highly performant but still needs some work. Please consider it experimental.

  • A much faster folding algorithm (See Bachetti+2020, ApJ) is now available, allowing to reduce the computing time of Z searches by a factor ~10, while simultaneously searching a 2D space of frequency and fdot. Select with --fast option

  • The classic Fast Folding Algorithm (Staelin 1969) is also available, to allow for extra-fast searches at low frequencies. However, this does not allow for “accelerated” searches on fdot. Also experimental and probably worth of further optimization.

Developed as part of CICLOPS – Citizen Computing Pulsar Search, a project supported by POR FESR Sardegna 2014 – 2020 Asse 1 Azione 1.1.3 (code RICERCA_1C-181), call for proposal “Aiuti per Progetti di Ricerca e Sviluppo 2017” managed by Sardegna Ricerche.


Lots of improvements to pulsar functionalities;


Windows support for Python <3.6 was dropped. Most of the code will still work on old versions, but the difficulty of tracking down library versions to test in Appveyor forces me to drop the obsolescent versions of Python from testing on that architecture.


The API is now rewritten to use Stingray where possible. All MPxxx scripts are renamed to HENxxx.

Functionality additions:

  • Epoch folding search

  • Z-squared search

  • Color-Color Diagrams and Hardness-Intensity Diagrams

  • Power spectral fitting

(MaLTPyNT) 2.0


MaLTPyNT provisionally accepted as an Astropy affiliated package

In preparation for the 2.0 release, the API has received some visible changes. Names do not have the mp_ prefix anymore, as they were very redundant; the structure of the code base is now based on the AstroPy structure; tests have been moved and the documentation improved.

HENexposure is a new livetime correction script on sub-second timescales for NuSTAR. It will be able to replace nulccorr, and get results on shorter bin times, in observations done with a specific observing mode, where the observer has explicitly requested to telemeter all events (including rejected) and the user has run nupipeline with the CLEANCOLS = NO option. This tool is under testing.

HENfake is a new script to create fake observation files in FITS format, for testing. New functions to create fake data will be added to hendrics.fake.

Preliminary notes

HENDRICS vs FTOOLS (and together with FTOOLS)


HENDRICS does a better job than POWSPEC from several points of view:

  • Good time intervals (GTIs) are completely avoided in the computation. No gaps dirtying up the power spectrum! (This is particularly important for NuSTAR, as orbital gaps are always present in typical observation timescales)

  • The number of bins used in the power spectrum (or the cospectrum) need not be a power of two! No padding needed.

Clarification about dead time treatment

HENDRICS does not supersede nulccorr (yet). If one is only interested in frequencies below ~0.5 Hz, nulccorr treats robustly various dead time components and its use is recommended. Light curves produced by nulccorr can be converted to HENDRICS format using HENlcurve --fits-input <lcname>.fits, and used for the subsequent steps of the timing analysis.


Improved livetime correction in progress!

HENexposure tries to push the livetime correction to timescales below 1 s, allowing livetime-corrected timing analysis above 1 Hz. The feature is under testing

License and notes for the users

This software is released with a 3-clause BSD license. You can find license information in the LICENSE.rst file.

If you use this software in a publication, please refer to its Astrophysics Source Code Library identifier:

  1. Bachetti, M. 2018, HENDRICS: High ENergy Data Reduction Interface from the Command Shell, record ascl:1805.019.

and please also cite stingray

In particular, if you use the cospectrum, please also refer to:

  1. Bachetti et al. 2015, ApJ , 800, 109.

If you have found a bug please report it by creating a new issue on the HENDRICS GitHub issue tracker.


(MaLTPyNT) 2.0

I would like to thank all the co-authors of the NuSTAR timing paper and the NuSTAR X-ray binaries working group. This software would not exist without the interesting discussions before and around that paper. In particular, I would like to thank Ivan Zolotukhin, Francesca Fornasini, Erin Kara, Felix Fürst, Poshak Gandhi, John Tomsick and Abdu Zoghbi for helping testing the code and giving various suggestions on how to improve it. Last but not least, I would like to thank Marco Buttu (by the way, check out his book if you speak Italian) for his priceless pointers on Python coding and code management techniques.

Getting started

Command line interface

API documentation

Indices and tables